504 



Prof. J. C. Bose. Influence of Electric 



both with heterodromous and homodromous currents, the testing stimulus 

 being either electrical or chemical. 



Reversal under Increased Heterodromous Current. 



Experiment 9. — In this the transmitted excitation due to the application of 

 salt, gave rise to an incomplete tetanus of moderate intensity. After securing 

 this condition, heterodromous current was applied and continuously increased. 

 It will be seen (fig. 10) that a great enhancement of conduction took place 

 when the current attained a value of 3 microamperes. A reversal was, 

 however, induced as soon as the current reached a value of 10 microamperes, 

 and we observe a complete cessation of normal incomplete tetanus. From 

 this we see that under reversal the conductivity is depressed below the 

 normal. 



Table VIII. — Showing Normal and Keversed Effects under Heterodromous 



Current. 



No. 



Intensity of current for 

 normal enhancement 

 of conductivity. 



Intensity of current for 

 reversed effect of depression 

 of conductivity. 





microamperes. 



microamperes. 



1 



1 -5 



6 



2 



1 -5 



8 



3 



2 



10 



4 



2 



10 



5 



3 



10 



6 



3 



10 -5 



7 



3 



11 



8 



3 



12 



Reversal under Increased Homodromous Current. 



Experiment 10. — On the appearance of incomplete tetanus T brought 

 on by the application of salt at the middle of the nerve, homodromous 

 current was continuously increased from zero to 10 microamperes and 

 then gradually brought back to zero. This was accomplished, as stated 

 before, simply by the forward and backward movement of the potentiometer 

 slide. The resulting record taken on the revolving drum shows the cycle 

 of effects. It is seen that the conduction in this case is arrested as soon as 

 the polarising current attains a value of 2 microamperes; at 10 micro- 

 amperes there is induced a reversal with an enhanced conductivity above the 

 normal. Under a continuous diminution of current there is an arrest of 

 conduction once more at 2 microamperes, and restoration of normal con- 

 duction at zero intensity of current. A continuous increase of current gives 



